[Miguel] it's easy for a
Portuguese-speaker to understand Spanish, but for an untrained Spanish-speaker,
it's relatively difficult to understand Portuguese.
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[Davius] What is the reason for this, Miguel?
Is the reason alike that this one: For any Peninsular Spanish speaker is relatively
easy to re-learn correctly any variety of American Spanish, because the
main phonetical differences consists of mergings, but I really know very few
latin americans that could reproduce without errors "th/s" alternances of
Peninsular (and that have merged in America).
In addition to the lack of symmetry in understanding we have
non-transitivity in mutually undertanding as dialect chains shows (although this
is not an argument against a "linguistic distances" in the same sense that the
lack of symmetry is an argument against it).
Davius Sanctex